The collection of visual images of vehicles as they move along a roadway has been found to be useful in an increasing number of applications. For example, the collection of visual images of vehicle license plates, along with images of vehicle types and/or colors, is useful in law enforcement to identify vehicles that exceed a speed limit and/or who otherwise violate traffic-related laws. When used in conjunction with other information, such as emissions data, vehicle inspection due dates, and other information, such images can be used to determine an individual vehicle's compliance with requirements such as emission requirements and inspection requirements. Such data can also be used for transportation systems planning. For example, the number of vehicles passing by a particular point over a time period may be collected, and such data may be compared to the visual images to determine the types of such vehicles, whether such vehicles exhibit in-state or out-of-state license plates, or other information. The prior art systems that provide for video capture of vehicle related information typically comprise analog video cameras placed along or near the side of a road. Such analog cameras feed collected visual images into a video capture card, which must be triggered, using software, to freeze the frame and commit the visual image into memory. The image is preferably digitized and compressed so that a larger number of images can be stored in a smaller amount of memory.
In some compression techniques, and especially techniques that start with analog images, the method of compression often results in degradation or loss of part of the original video image. In such a situation, if the license plate number and/or state is not legible in the stored image, the image cannot be used. In addition, many applications require more than just a license plate number, such as information relating to vehicle manufacturer, color, and/or type, which are all additional items of information which can be lost in the compression process.
In addition, the method of using an analog camera and capture board is expensive, as many pieces of equipment are required to accomplish the result. Further, many of the prior art video capture cards generally can handle only one camera. Accordingly, they are not desirable in applications where multiple cameras are required, such as in areas where multiple cameras are used to collect data across multiple lanes of a roadway.
Accordingly, it is desirable to provide an improved method and system for the capture of visual information relating to vehicles traveling on a roadway.